Mets catcher John Buck suffered a cramp in the eighth inning of last night’s 13-8 loss to the Phillies. He stayed in to finish the game, but manager Terry Collins said the veteran will get the day off today and will return to the lineup tomorrow.

“It was just on my one swing,’’ said Buck, who grounded out to shortstop Jimmy Rollins to end the game. “I felt it defensively the inning before.’’

Buck said he should be fine to start tomorrow in the series finale.

“I’ll be OK,” he said. “I tried to convince Terry I’ll be fine [today], but he’s the boss.’’

* Jeremy Hefner’s career 13.75 ERA (28 earned runs in just 18 1/3 innings) against the Phillies is the fifth-worst of any pitcher against one team since 1921. Against every other squad, he has a 3.54 ERA.

The seven runs the Mets allowed in the third was the most they’ve given up in any inning this year. … Reliever Greg Burke surrendered three walks and four earned runs in just 2 2/3 innings, and has allowed a dozen runs — 10 earned — in 13 innings (spanning 13 games) dating back to May 31. … Daniel Murphy went 1-for-3 with a run and an RBI, and is batting .302 on a nine-game hitting streak that dates back to July 6 in Milwaukee.

* Lucas Duda has started to hit, but the Mets still aren’t sure how long he’ll have to spend in the minors or when he’ll be ready to return to the big leagues. Collins said it largely depends on whether Ike Davis — who went 2-for-4 last night to raise his average to .171 — ever breaks out of his funk, but acknowledges he has no clue what the club’s long-term plan is for Duda.

“Nothing has been discussed on Lucas,’’ Collins said. “I really don’t know what the long-range plan’s going to be. A lot may depend on if Ike starts hitting — that may have something to [do with it]. If Ike doesn’t start hitting, that will have something to do [with it]. It certainly has not been discussed where Lucas is going to stay when he’s ready to play.’’

Duda was hitting .235 with 11 homers and 23 RBIs in 68 games before going on the disabled list June 22 with a left intercostal strain.

Justin Turner headed to Brooklyn last night to continue his rehab assignment. Since he hasn’t had that many at-bats, and the Mets have used their bullpen so much, Collins opted to go with an extra reliever through the weekend.

“I’d probably say Atlanta [Monday] would be more likely,’’ Collins said of a possible return for Turner, on the DL also with an intercostal strain. He’s hitting .266 with six RBIs. … Jon Niese, on the DL since June 21, is long-tossing and close to getting back on the mound.